The present invention relates generally to retraction mechanisms for utility supply lines and more particularly to a dental unit or the like wherein fluid pressure is utilized to retract a utility supply line connected to a dental instrument.
It is well known in dental units to have a dental instrument nested in the unit and connected by a cord, hose, etc. to a utility supply. It is desirable in such units to provide a mechanism for retracting or pulling the extended utility supply line back into the dental unit, when the dental instrument is being returned to a storage position. This not only provides a neat appearance to the dental office, but also free-hanging cords or other utility supply lines may be disturbing to the patient.
Various retraction mechanisms are known which allow for the extension of the utility line out of the unit when the instrument is being moved to an in-use position and which serve the purpose of automatically retracting the utility supply line back into the dental unit when the instrument is returned to a storage or out-of-use position.
For example, such retraction mechanisms may operate by gravity. Here the utility line may pass over a system of pulleys and counter weights which move under the influence of gravity to provide the retraction force. Other systems may utilize a spring force for retracting the utility lines. All these systems, however, have the inherent disadvantage that the operator must pull on the dental instrument with force in order to overcome the retraction force. Such systems also require that the retraction mechanism be locked in order to eliminate a constant strain on the utility line, when the dental instrument is in a position of use.
Other retraction systems may utilize motors for driving a re-wind reel or other retraction mechanism but these have the disadvantage of having a relatively high initial cost.
Still other retraction systems are known which utilize a fluidic pressure to provide the retraction force. Such systems are shown for example in U.S. Pat. Nos. 3,722,095, 3,427,719, and 3,391,875. However, the fluid operated systems shown in all of these patents depend upon the action of a piston for transmitting the applied fluid pressure into motion for retracting the hose. Further, the systems disclosed in these patents have the utility supply line looped about pulleys which increase the length of the loop for retracting the supply line, but make no provisions for changing the shape of the loop. Pulley guided systems also have the disadvantage that care must be taken to prevent the utility line from slipping off of the pulley during operation.
The present invention provides a fluid operated retraction system which eliminates all of the drawbacks of the prior art, in that the fluid pressure for imparting motion to the utility supply line, operates directly on the utility line. This eliminates the need for any pulley or piston system, and also greatly reduces the space and cost requirements, as well as the number of components involved in making the system operative.